Mechanical pipe couplings have found wide commercial acceptance in various industries. However, it has been desirable to increase the ease of assembly of the coupling and to enhance its resistance to unauthorized tamperings. There have been many prior attempts to resolve these problems, but none have been fully successful.
For example, U.S. Pat. No. 2,362,454, to Damsel, issued Nov. 14, 1944, discloses a pipe coupling in which the coupling segments are held in assembled condition by locking pins which extend through lugs at the ends of the coupling segments. In Damsel, assembly of the coupling is effected by means of a chain-type pipe wrench, which must be assembled about the pipe and requires a chain to be properly attached to a traction mechanism and then be placed in encircling relationship with the coupling segments. The use of such a chain-type pipe wrench in locations having limited access poses substantial problems, particularly as the wrench must be applied to the coupling segments at the time they are freely movable on the pipe exterior and unsecured relatively to each other. The workman must thus not only hold the arcuate segments in position on the pipe, but also must simultaneously position the chain of the pipe wrench over the coupling segments and hold the assemblage assembled during closure of the pipe wrench.
A more conventional closure arrangement is disclosed in U.S. Pat. No. 3,054,629, to Piatek, issued Sept. 18, 1962 in which the coupling segments are held together by bolts which are passed through bolting pads at the ends of the coupling segments. While tampering can be effected by loosening the bolts using a commonly available wrench, the construction is significantly less complicated to assemble than the more tamper resistant structure of Damsel U.S. Pat. No. 2,362,454.
It has also been proposed, to employ toggle means as a closure device for the coupling segments. For example, in U.S. Pat. No. 2,752,174, to Frost, issued June 26, 1956, a pair of coupling segments are hinged to each other at one of their ends, and a toggle linkage and a camming lug are provided at their opposite ends for use in closing and locking the coupling. This construction, while materially aiding in the assembly of the coupling, requires that the coupling segments be dissimilar in shape and that the toggle linkage be an integral part of the coupling. Further the ease of assembly results in a co-related ease of disassembly and no means are provided for locking the toggle linkage. Thus, the coupling is readily susceptible to tampering.
In U.S. Pat. No. 3,825,403, to Perrin et al, issued Aug. 13, 1974 identical coupling segments are closed by a toggle linkage which is integral with the coupling. Once closed a separate pin is provided for locking the toggle linkage against accidental release. However, the problem of tampering still remains since the toggle mechanism remains in place, and the locking pin is not under any significant shear load such as would make it difficult to remove. U.S. Pat. No. 4,272,871, to Weinhold, issued June 16, 1981, suggests that identical coupling segments which are secured by a toggle linkage be provided with bolts for securing the respective coupling segments to each other at their adjacent ends to maintain the coupling closed in the event that the toggle linkage is released. Since the toggle linkage remains secured to the mated ends of the coupling segments in a permanent fashion, each coupling requires its own toggle linkage.
In U.S. Pat. No. 3,744,825, to Cooper et al, issued July 10, 1973, closure is effected by a separate tool. While the structure proposed by Cooper et al eliminates the need for a permanently attached toggle linkage, it also precludes the possibility of forming the coupling of identical segments. Further, the discontinuous profile in Cooper et at does not permit the use of a continuous sealing gasket.